Terminal construction



Sept 30, 1941 N. c. SCH'ELLENGER 2,257,621

TERMINAL CONSTRUCTION Filed March 8, 1959 2 Sheets-Sheet l ATTORNEY Sept. 30,- 1941.

N. c. SCHL-:LLENGER 2,257,621

TERMINAL CONSTRUCTION Filed March 8, 1939 ATToRNEY.

Patented Sept. 30, 1941 TERMINAL CONSTRUCTION Newton C. Schellenger, El Paso, Tex., assignor to Chicago Telephone Supply Company, Elkhart, Ind., a corporation of Indiana Application March 8, 1939, Serial No. 260,545

(ci. zal-s3) 14 Claims.

This inventionrelates to a new and improved terminal construction and more particularly to such a construction adapted for use in connection with variable resistance devices.

My invention is especially applicable to variable resistance units employing resistance strips of carbonaceous type. Such units in general comprise a non-conducting base, with a resistance strip secured to the base, the strip consisting of a non-conducting support and a thin layer of conductive material sprayed or painted upon the upper face of the supporting material. The conductive layer usually comprises iinely divided conductive material such as some form of carbon together with a binder and in some cases iinely divided non-conducting material may also be included.

- The variable resistance device includes a movable contact driven by a rotary shaft and a plurality of terminals by which the unit may be connected into the electrical circuit with which it is used. In some cases this may involve `merely two terminals, one connected to the movable contact and the other to one end of the resistance strip. In other cases there is an additional terminal connected to the other end of the resistance strip. Some uses of the device require one or more additional tap terminals connected to intermediate portions of the resistance strip. Such uses occur in radio apparatus where it is desired to connect portions of the circuit to the resistance to provide a fixed bias or a potential difference between such portions of the circuit and portions connected to the end or ends of .the resistance strip.

In many cases such taps must be electrically connected to portions of the resistance strip spaced a substantial distance from .the end terminals. Where the tap terminal is located at the same point as the electrical tap, an extra extension of the base is required which increases the size of the device. Also in present day compact assemblies there may be dilculty in sopositioning the device that wires may be readily soldered to the terminals at widely spaced points upon its periphery. It is therefore desirable to locate the tap terminal or terminals adjacent the other terminals of the unit even if the electrical tap connection is spaced from the terminala Terminals when secured to the base of the unit are located closely adjacent the supporting chassis when the unit is secured in place upon the chassis. This location may be undesirable cult to get at for solderingin compact assemblies. There is danger of shortlng the terminals due to their becoming bent or due to excess solder. Also there may be undesirable capacity coupling between the terminals and a grounded metal chassis.

It is an object of this invention to provideY a new and improved terminal construction adapted for use upon a tapped control in places where space limitations make it diflicult or impossible to use an ordinary type of tap terminal construction.

Another object is to provide a construction in which contact between a tap and the conductive surface of a resistance element is maintained under pressure by the housing assemblies.

It is a further object to'provide a construe1 tion which facilitates the assembly of a cover and insulating means in connection with a terminal.

It is also an object to provide a construction wherein a plurality of independent taps may be used at one time on a single device with the tap terminals located adjacent each other.

It is an additional object -to provide a standard construction by which taps may be selectively connected to one of a plurality of portions of the resistance with the tap terminal in a single prem determined position.

It is a further object to provide a construction in which terminals may be secured in position without the use of separate securing means.

Other and further objects will appear as the description proceeds.

I have shown certain preferred embodiments of my invention in the accompanying drawings, in which- Figure 1 is a face view of the variable resistance device with the cover partly broken away;

Figure 2 is an elevational view of the construe tion of Figure 1 showing the tap construction on the variable resistance device;

Figure 3 is a section taken on the line 3-3 of Figure i, showing one form of insulator;

Figure 4 is a fragmentary section similar to Figure 3, showing another form of insulator;

Figure 5 is a fragmentary elevation of the insulator shown in Figure 4;

Figure 6 is a face view of a variation of a tap I0 construction with the cover of the variable resistance device removed and the resistance element partly broken away;

Figure 7 is a plan view of the insulator shown in Figure 3:

for several reasons. Such terminals may be dimu Figure 8 is a plan view of the tap connecting conductor with modifications represented in dotted lines;

Figure 9 is an enlarged fragmentary section of a modified form of terminal construction;

Figure 10 is a fragmentary plan view partly in cross-section, taken on the line III-III of Figure 9;

Figure 11 is a fragmentary elevation of the construction shown in Figure 9, as seen from the left;

Figure 12 is a fragmentary section of another modification of the terminal construction; and

Figure 13 is a fragmentary section of a form of construction oi terminal adapted for use in connection with a movable contact.

Referring first to Figures 1 to 8, inclusive, the improved tap construction comprises a conductor II which may be formed from thin metal foil, such as copper, or other material having conductive properties. This conductor is positioned between the base I2 of the resistance device and the nonconductive face of the resistance element I3. This resistance element com.- prises a body of Bakelite, fibre or other nonconducting material with a resistance lm or coating upon its upper face. In the present embodiment, the conductor is arcuate in shape and is adapted to under-lie the outer portion of the resistance element. The conductor is secured to the base I2 at one end by means of the solder lug terminal I4 and the rivet I5. The terminal is secured to an extended portion I6 of the base I2. The other end of the conductor Il comprises a laterally offset narrow portion I1 which is wrapped around a projection I8 of the resistance element I3 so -that the end of the portion I1 lies upon the conductive face of the resistance element. The resistance element is provided with additional tap extensions I8-A and IB-B and, as shown in Figure 8, the conductor Il may be made in suitable lengths for the different tap extensions as shown in broken lines at I1-A and I1B.

The cover I9 is provided with a plurality of securing lugs 20, which intert in the notches 2| in the edge of the base I2. The securing lugs are bent against the under face of the base or against a grounding plate 22 which may be provided to ground the cover to the metal bushing 23 which is secured to the base I2 and provides a bearing for the rotary shaft 24. This shaft 24 has the non-conducting drive plate 25 connected thereto and this plate drives the movable contact member 26. 'I'he member 26 is provided with the portions 21 engaging the upper face of the resistance element I3 and the portions 28 engaging the collector ring 29. The collector ring is provided with the terminal 65 and the ends of the resistance strip I3 have the fixed terminals 66 and 61 secured thereto. The details of construction of the variable resistance device are disclosed in my prior application, Serial No. 218,062, filed July 8, 1938, and form no part of the present invention. The lugs, as well as the notches in the base, are so positioned that one of each falls on either side of such points as the projections I8, I8-A and I6-B and ends I1, I1-A or I1-B of the conductor II may be located. Other lugs and notches may be located elsewhere as required for holding the cover in place. The side wall of the cover is cut out between the lugs adjacent the projections I8, I8A and I8-B to a height approximating thecombined thickness of the base I2,

the resistance element I8 and the insulator 30. as shown in Figures 2 and 3.

The insulator 30 may be formed Iiorn a strip of Bakelite, fibre or other non-conductive matorial. It will be noted that the notches 3| and projections 32 are substantially wedge-shaped. The notches provide recesses to receive the lugs 20, and the projections 32 fit between the cover lugs at the upper part oi the cut-out portions of the cover side wall. The inclined sides oi the projections 32 prevent the insulator from becoming disengaged from the cover during assembly.

When assembled, the cover I9 is tightly held in place by the lugs 2U, which are positioned within the notches 2I and are bent under the base. The bottom edges of the cut-out portions of the cover side wall exert pressure on the projections 32 of the insulator, and the insulator in turn bears down on the end I1 of the conductor II which lies upon the upper face of the projection I8 of the resistance element. The under surface of the conductor I1 is held in close contact with the projection I2 of the base. It is desirable to have a slightly convex curvature to the bottom of the cut-out portion 33 of the cover side wall so that a greater pressure will be applied at the center of the insulator projection 32 than at its edges. The form of construction shown in Figure 6 provides for two tap terminals upon a unit at the same time.

A modified form of insulator, as shown in Figures 4 and 5, comprises a strip of flexible insulating material 34 of suiiicient length to completely encircle the inside of the side wall of the cover or housing. It is desirable that the insulating material have sufilcient resilience to maintain its position within the cover, although other securing means may be employed. The strip 34 has notches 35 in alignment with those of the side wall; these notches, however, are not as deep as those of the side wall, consequently when the cover is in position the upper edge of the strip 34 is in contact with the top of the cover, and the lower edge of the notches 35 exert a pressure on the conductor I1, as described in connection with the insulator shown in Figure 7. It will be noted that the lower edge of the insulator notches 35 are slightly convex for the purposes set forth in connection with the cut-out portions of the cover side wall as shown at 33 in Figure 2.

Referring now to the form of terminal construction shown in Figures 9 to 11, an insulating plate 36 is placed upon the outer face of the metal cover 31 of the resistance device. A switch housing 38 is shown above the plate 36 and the means securing the switch in place serve also to retain the plate in position. The construction may be used independently of the switch, however. The plate 36 has an extended portion 33 which projects beyond the side walls of the cover at such point as a terminal lug 40 may be positioned. The solder lug portion 4I of the terminal 40 projects through a slot in the extended portion 39. 'I'his slot is sufliciently wide to allow the head of the lug to pass through, but the shoulder 42 abuts against the under side of the portion 39 and retains the parts in proper position. Above the shoulder 42 is a second shoulder 43 having a width approximating that of the slot and which positions the lug in the slot. The terminal 40 is formed of sheet metal, and has an integral contact portion 44.

The contact portion of the terminal 40 is folded inwardly under the insulating segment 45, and the end 46 of the terminal is bent upwardly against the inside oi the segment. The notches 41 and 48 in the segment 45 provide locating recesses for the terminal 40 and serve as a means for positioning the terminal with respect to the assembly. The notch 41 in the forward edge of the segment may be deeper than the thickness of the conductor, while the notch 48 in the rear edge is preferably equal to the thickness of the conductor. The segment also has shoulders 49 which rest against the outside of the cover 31 and prevent the segment from moving inwardly toward the metal cover 31. The under surface of the contact portion 44 is held in engagement with the conductive coating of the resistance element I3, which in turn is supported by the base I2. The base and resistance element have projections extending beyond the side wall of the cover at such point as the tap may be positioned, and serve as a support therefor.

The cover 31 has a cut-out portion 50 of a width approximating the distance between the shoulders 49 and a height equal t0 the combined thickness of the conductor 44 and the insulating segment 45. The cover, as shown in Figures 9 and l0, is provided with an insulating strip I which fits within the side walls of the cover, as described in connection with insulation strip 34 of Figure 5. The strip has notches corresponding to those in the cover and aids in holding down the segment 45. The upturned end 46 of the terminal 40 engages the inner face of the insulating strip and thus prevents the terminal and segment from moving outwardly. The cover has securing lugs 52 which interit in notches in the base, and are bent against the under face of the base I2 to maintain the parts in assembled relation.

The embodiment shown in Figure l2 is somewhat similar to that shown in Figures 9, and il. The terminal 53 is positioned within the cover 54 and the solder lug portion 55 projects through an opening 56 in the top of the cover. rl'he insulating plate 51 is retained against the under side of the cover by the insulating strip 58 which also serves to insulate the terminal from the side wall of the cover. The lower end 59 of the terminal 53 is folded outwardly under the insulating segment 45 and the end is bent upwardly against the outside of the segment. The assembly isheld together as set forth in respect to Figure 9.

Figure 13 shows a construction similar to that in Figure 9, as applied to the center terminal of a variable resistance device. The variable resistance device is similar to that shown in Figures 1 and 3. The center terminal 60, as shown, is formed integrally with a collector ring member 5I at its lower end and a solder lug portion 62' at its upper end. The intermediate depressed portion of the terminal nts in a cut-away portion of the base and maintains the parts in desired relation by preventing both radial and circumferential movement of the terminal. In this construction the resistance element does not have a projection overlaying the projection of the base I2, the conductor being held in direct contact with the base. In other respects the assembly is as described in connection with Figure 9.

While the constructions of Figures 9 to 12 show only s. single terminal it will be understood that these forms of construction may be applied to a plurality of terminals in a single unit. This form of construction, together with that of Figure I3, may be applied to all of the terminals of a unit to provide a device especially adapted for use where space is limited or where for any reason it is desired to have the terminals located above the housing for easy access.

All the forms of construction shown may be used to provide devices with tap connections,

which devices are smaller in overall dimensions than devices with the tap terminal located at the point of electrical connection of the tap. rIihe constructions all may be used to group the terminals to facilitate wiring or to so locate all terminals as to maintain them spaced from other.

elements of the circuit to minimize coupling of any kind. The constructions are also so designed as to provide a irm and permanent engagement between the resistance element and the terminals. This affords an efficient connection without the use of rivets which add to the cost of the device.

While I have shown certain preferred forms of construction, these are to be understood to be illustrative only, as the devices are capable of change and modification to meet varying conditions and requirements and I contempla-te such variations as come within the spirit and scope 0f the appended claims.

I claim:

l. In a resistance deviceof the character described: a base; a resistance element on the base having an exposed conducting surface; a cover for the resistance device, positioned over vsaid base and the resistance element; a terminal having an external part to which leads may be secured and having a portion engaging an area of the exposed conducting surface of the resistance element where the resistance element is supported by the base; an insulator engaging said portion of the terminal so that said terminal portion is interposed between the insulator and the conducting surface of the resistance element, part of said cover engaging the insulator directly over the contacting portions of the terminal and resistance element and consequently over the support provided by the base so that pressure on the cover toward the base clamps the-terminal portion against the resistance element and establishes good electrical connection therebetween solely by the attachment of the cover to the base; and means for drawing the cover and base together and holding the same assembled.

2. In a resistance device of the character described: a base; a resistance element on the base; a cover for the resistance device disposed over the base and the resistance element, said cover having a side wall; a terminal for` the resistance element having a portion electrically and physically contacting the same; an insulator between the side wall of the cover and the terminal portion which contacts the resistance element so that pressure applied to the insulator by the side wall holds the terminal firmly to the resistance element; a second insulator supported by the cover and engaging another portion of the terminal to position the same; and means for maintaining a side Wall of the cover in contact with the iirst named insulator under pressure.

3. In a resistance device of the character described: a base: a resistance element on the base and having ank exposed conducting surface; a cover for the resistance device disposed over the base and the resistance element, said cover having a side wall; a metal terminal strip having a portion in electrical contact with the exposed conducting surface of the resistance element and having an outer end portion extending out past the side wall; an insulator coniined between the side wall and the rst named portion of the terminal strip to hold the terminal strip on the resistance element; a second insulator supported by the cover and engaging the outer end portion of the terminal strip to position the same; and means for drawing the cover down onto the base and thereby clamping the first named insulator between the cover side wall and the terminal strip to press the terminal strip against the conducting surface of the resistance element.

4. In a resistance device of the character described: a base; a resistance element on the base and having an exposed conducting surface; a cover for the resistance device disposed over the base and the resistance clement, said cover having a-top and a side wall; an insulator within` the cover overlying its side Wall and abutting its top, the side wall and said insulator within the cover having aligned notches in their edge portions adjacent to the base with the notch in the side wall deeper than the notch in the insulator; a terminal member having a portion passing through the aligned notches and engaging the exposed conducting surface of the resistance element with a part thereof conned between the resistance element and the bottom of the notch in the insulator; and means for drawing the cover to the base to thereby press the terminal member against the exposed conducting surface of the resistance element and thus hold the terminal and resistance element together with a good electrical connection established therebetween solely by the attachment oi the cover to the base.

5. A terminal construction for resistance devices comprising a base member, a cover for the base member having a top and side wall, an insulator within said cover overlaying said side wall and abutting said top, said insulator and side wall having cut-away portions in their margins adjacent to the base, a terminal member having an extremity entering said cut-away portion, a second insulator overlaying said terminal extremity and having a portion entering said cut-away portion, said second insulator having shoulders abutting the outside of said side wall and providing positioning means inside and outside of said side wall for said terminal extremity, and means cooperating with said cover and base for maintaining said first named insulator in contact with said second named insulator.

6. In a resistance device of the character described: a base of insulatin lr material; a resistance element on the base, said resistance element having an exposed conducting surface; a substantially cup-shaped metal cover for the resistance device positioned over the base and the resistance element with the side wall of the cover engaging the base; a metal terminal having a portion overlying a small area of the conducting surface of the resistance element and having a part to which external leads may be attached, said portion of the terminal being adjacent to the side wall of the cover; an insulator overyling said terminal portion, part oi the cover engaging the insulator directly over the contacting portions of the terminal and resistance element so that pressure on the cover toward the base clamps the insulator, the terminal portion, and the adjacent portion of the resistance element between the cover and the base and establishes good electrical connection between the terminal and resistance element solely by the attachment of the cover to the base; and means on the side wall of the cover engaging the base adjacent to the contacting terminal and resistance element portions and drawing the cover tightly toward the base.

7. In a resistance device of the character described: a base of insulating material; a substantially arcuate resistance element on the base having an exposed conducting surface; a substantially radial extension projecting outwardly from the resistance element. the exposed surface of theextension being electrically conductive and forming substantially a continuation of the conducting surface of the resistance element; a substantially cup-shaped cover engaged over the base and the resistance element and having a side wall disposed over and across the radial extension on the resistance element, the base having a portion thereof supporting said extension of the resistance element; a metal terminal having a portion engaging the conducting surface of said radial extension and having means to which external conductors may be attached; an insulator interposed between a part of the cover and said portion of the terminal and disposed over the contacting portions of the terminal and resistance element to press the terminal against the conducting surface of the resistance element and clamp the terminal and said radial extension of the resistance element between the insulator and the base upon the application of force on the cover toward the base; and means for drawing the cover tightly against the base to thereby hold said parts assembled.

8. In a resistance device, a base having an extended portion thereon, a resistance element I overlaying said base, a cover for said device, an insulator overlaying said cover and having an extended portion, a terminal member having its lower extremity in contact with said resistance element, a second insulator overlaying the lower extremity of said terminal member adjacent to the extended portion of said base, means provided by the extended portion of the iirst named insulator for positioning the upper end of said terminal member, and means associated with said cover and said base for maintaining contact of said terminal element with said resistance element.

9. A terminal construction for an electrical control device having a base, a current carrying part on the base, and a cover disposed over the base, comprising: a metal terminal strip having a portion thereof physically and electrically contacting the current carrying part and having an outer end portion; insulated means for definitely positioning the outer end portion of the terminal strip with relation to the cover; non-conducting means engaging the terminal strip portion which engages the current carrying part and adapted to be pressed against said portion of the terminal strip by the cover upon its securement to the base; and means for securing the cover to the base.

10. In a resistance device of the character described: a resistance element on the base having an exposed conducting surface; a terminal having a part engaging said conducting surface; a cover for the device disposed over the base and the resistance element and having a notch in its edge adjacent to the terminal so as not to contact the same; an insulator engaging the terminal and having a projection disposed within said notch to be confined between the bottom of the notch and the terminal; and means for drawing the cover to the base to clamp the terminal against the resistance element.

il. In a resistance device oi the character described: a base; a resistance element on the base and having a projection thereon overlying the base; a conductor between said resistance element and the base and having an extremital m described: a base; a resistance element on the base and having an exposed conducting surface; a terminal member having a part engaging said conducting surface; a cover for the device disposed over the base and the resistance element thereon and having a part thereof crossing the terminal adjacent to its portion which engages the exposed conducting surface of the resistance element; an insulator interiltting with the cover and having a convex surface engaging the terminal member to press the same against the resistance element; and means for drawing the cover to the base so as to apply pressure on the insulator for pressing the terminal membe against the resistance element.

13. In a resistance device of the character described: a base; a element overlying the base and having an outward projec- 40 tion thereon; a terminal for the resistance element having a part wrapped about said projection to dispose a part thereof between the projection and the base and another part thereof over the projection of the resistance element; a cover for the resistance device disposed over the base with a part thereof crossing said projection; a pressure applying non-conducting connection between the cover and the part of the terminal disposed over the projection on the resistance element; and means for drawing the cover to the base to press the terminal against said projection to establish good electrical connection therebetween and also clamp said projection against the base to thus hold the resistance element and the terminal to the base at the location of said projection.

14. In a resistance device of the character described: a base of insulating material; a resistance element on the base having a nonconducting bottom and a conducting top surface; a projection on the resistance element; a terminal strip disposed between the non-conducting bottom surface of the'V resistance element and the base, part of said terminal strip being folded over said projection to engage the top conducting surface thereof; a cover for the resistance device disposed over the base and resistance element. said cover having a part adapted to press the folded portion of the conductor firmly against the conducting surface of the resistance element projection upon attachment of the cover tothebase;meansfordrawingthecoverto the base; and a terminal part on the conductor remote from its portion which is folded over the projection on the resistance element and extending outside the cover for the attachment of leads thereto.

NEWTON C. GER. 

